AU694827B2

AU694827B2 - Radiating H.F. cable arrangement

Info

Publication number: AU694827B2
Application number: AU42056/96A
Authority: AU
Inventors: Mark Davies
Original assignee: Alcatel NV
Current assignee: Alcatel Lucent NV
Priority date: 1995-02-03
Filing date: 1996-01-19
Publication date: 1998-07-30
Anticipated expiration: 2016-01-19
Also published as: DE19503440A1; NZ280837A; DE19503440C2; AU4205696A

Description

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ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "RADIATING PIE CABLE ARRANGEMENT" The following statemnent is a full dlescription of this invention, including the best method of performing it known to uIS:- -7~T----C-C14C I L 2 This invention relates to an arrangement for transmitting, radiating and receiving high-frequency signals, of the type consisting of a radiating first coaxial highfrequency cable with an outer conductor which has openings over its whole length, and a second coaxial high-frequency cable with a closed outer conductor arranged parallel to the first coaxial cable. The two high-frequency cables are each connected by one end to a common transceiving station for high-frequency signals and electrically connected to each other at least at one point in their length.

Radiating high-frequency cables referred to below as "RHF-cable" are used 10 for example within the framework of mobile telephone systems, where a leo• S communication link is desired between a fixed station and a mobile station. Railway tunnels are a particular field of application, in which a wireless radio transmission is not possible or is only possible with limitations. Due to the openings in the outer e ee conductor, HF energy can be received or coupled into the outer conductor by means of suitable aerials at each point of such a RHF cable. However, the HF signals are 0054 highly attenuated by this design. In longer lengths of tunnel, intermediate repeaters have to be inserted in the transmission section. The intermediate repeaters are in addition not only active components with a separate electrical power supply, but they must be maintained and if necessary replaced. In railway tunnels that can lead to difficulties.

The known type of arrangement mentioned at the beginning is meant to avoid that. In this well-known arrangement, two coaxial HF cables, with an inner system and an outer system, are used connected to one cable. The inner system consists of a coaxial HF cable with a closed outer conductor. The outer system is a RHF cable arranged concentrically to the inner system, its inner conductor being the outer cable of the inner system. At intervals there is capacitive or inductive coupling of both systems to each other. Although the HF signals are transmitted with small losses in the inner system, the range of this arrangement is limited without repeaters, since the inner system has high attenuation, especially at high frequencies, due to its comparatively small dimensions.

It is an object of the present invention to improve the arrangement described at -7 II 3 the beginning so that a greater range is obtained.

According to the invention there is provided an arrangement for transmitting, radiating and receiving high frequency signals of the aforementioned type, wherein the second HF cable having a markedly larger diameter than the RHF cable; the RHF cable being divided into at least two sections, which are arranged in tandem in the axial direction, and of which a first section is connected to the transceiving station; and the second HF cable being, with the exception of the first section, connected by the given electrical coupling respectively with at least one of the sections of the RHF cable.

In this arrangement the HF signals are transmitted with small losses in the second HF cable, actually due to its large dimensions even at higher frequencies and high frequencies. HF signals coming from the transmitter are fed into the coupling points using variable power preferably in each of the two sections but at least in one section of the RHF cable, so that HF signals can always be transmitted at a sufficiently high level along these sections. The range of the transmission can thereby be increased without using intermediate repeaters, even if several coupling points between both HF cables are available in the length of the transmission section. The transmission of the HF signals is more reliable. Upkeep for active components is no longer necessary. All this also applies analogously to a vehicle's HF signals fed into the RHF cable.

In order that the invention may be readily carried into effect, embodiments thereof will now be described in relation to the accompanying drawings, in which: Fig. 1 shows the arrangement according to the invention in a diagrammati, view.

Fig. 2 shows part of cin arrangement modified with regard to Fig. 1.

Figs. 3 and 4 show, in enlarged representation, details of the arrangement in two different forms of design.

The arrangement shown in Fig, 1 with a radiating first coaxial HF cable, the RHF cable 1, and a second coaxial HF cable with a closed outer conductor, the HF cable 2, is to be arranged in a length of tunnel for rail vehicles. Both cables 1 and 2 -1 I LI -JF

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4 are connected to a transceiver station 3 situated outside the tunnel and which can be equipped with an aerial 4.

RHF cable 1 and HF cable 2 run parallel to each other, in fact as close as possible alongside each other. The HF cable 2 has a markedly greater diameter compared with the RHF cable 1. The diameter preferably is approximately twice as large as that of the RHF cable 1. The HF signals can also be transmitted from there at very high frequencies with considerably smaller losses via the HF cable 2 than via the RHF cable 1.

The RHF cable 1 for example can be a 15/" cable, while a 3" cable for example is used for the HF cable 2. For example, at a frequency of 1900 MHZ (earth network eg. PCN of the HF signal to-be-transmitted, these ccules have a typical longitudinal attenuation of about 66 dB/km for the RHF cable 1 and about 21 dB/km for the HF cable 2.

The RHF cable 1 is subdivided into sections 5 and 6, which for example have a length of 700 m. The number of sections 6 is dependent on the length of the tunnel section. At least one section 5 and one section 6 are installed in the tunnel. The first section 5 of the RHF cable 1 is directly connected to the transceiver station 3. Two sections 6 are each connected electrically at the coupling points 7 to the HF cable 2.

'2U But each section 6 could also be individually electrically connected to the HF cable 2.

In a preferred form of design, the first section 5 of the RHF cable 1 and the HF cable 2 are connected in accordance with Fig. 2 to the transceiver station 3 by insertion of a power splitter 8.

In the coupling points 7, HF signals coming from the transmitter S of the transceiver station 3 are fed from the HF cable 2 into two adjoining sections 6 of the RHF cable 1. The HF signals can then be received along the two sections 6 by means of a suitable aerial. HF signals fed from a vehicle into the sections 6 are coupled into the HF cable 2 via the coupling points 7 and transmit from the said HF cable 2 lossfree to the receiver E of the transceiver station 3. With a longer length tunnel, a greater number of sections 6 of RHF cable 1 are as already mentioned arranged in tandem. The number of coupling points 7 is increased accordingly.

A coupling point 7 can be designed for example according to Figs. 3 and 4: I L_ The HF cable 2 is cut in the locality of the coupling point 7. A power splitter 13 is inserted in the HF cable 2 via commercially-available HF connectors 9 and 10 and incircuit flexible lengths 11 and 12 of coaxial HF cable. The HF cable 2 is thereby conductively reconnected. A portion of the power of the HF signal to be transmitted is decoupled by the power splitter 13 designed for example as a 3dB coupler and supplied via an additional length 14 of flexible coaxial HF cable to a second power splitter 15 which again can be designed as a 3dB coupler. Two sections 6 of the RHF cable 1 are connected to the power splitter 15, in fact via flexible lengths 16 and 17 of coaxial HF cable and commercially-available HF connectors 18 and 19.

This lay-out of the coupling points 7 is advantageous in that the same power is 4*t* decoupled at each coupling point. At the beginning of the length, and therefore in the vicinity of the transceiver 3, commensurately little energy is decoupled from the HF cable 2 as at other remote coupling points 7.

The design of the coupling point 7 at the end of the transmitting section is S simplified as follows from Fig. 4..Since the HF cable 2 cannot be through-connected, S the components 10 and 12 are omitted. A similar simplified design of the coupling point 7 then results, if only one section 6 of the RHF cable 1 is always connected to the HF cable 2. However, the number of coupling points 7 is then increased.

The entire coupling point 7, consisting of power splitters, lengths of HF cable and HF connectors, can be prefabricated. It then only requires to be fitted during installation of the RHF cable 1 and HF cable 2. It is particularly easy if lengths of flexible HF cable are used. However, in principle, less pliable HF cable lengths can also be used. If power splitters are used with the so-called "back-to-back" outputs, the connecting lengths of cable can be completely dispensed with.

To complete the picture, mention is made that in very long sections of tunnel at least one repeater can be inserted in the HF cable 1. However this does not alter the advantageous arrangement described, which fundamentally does without active components in the RHF cable sections.

Claims

1. An arrangement for transmitting, radiating and receiving high-frequency signals, the said arrangement consisting of a radiating first coaxial high-frequency cable with an outer conductor which has openings over its whole length, and a second coaxial high-frequency cable with a closed outer conductor arranged parallel to the first coaxial cable, in which the two high-frequency cables are each connected by one end to a common transceiving station for high-frequency signals and electrically connected to each other at least at one point in its length, wherein, the second high-frequency cable has a markedly greater diameter than the radiating high-frequency cable, the radiating high-frequency cable is subdivided into at least two sections which are arranged in tandem in the axial direction, and of which a first section is connected to the transceiving station, and the second high-frequency cable is, with the exception of the first section, connected by the given electrical coupling respectively with at least one of the sections of the radiating high-frequency cable.

2. An arrangement as claimed in Claim 1, wherein the diameter of the second 'i"C high-frequency cable is approximately twice as large as that of the first high- frequency cable.

3. An arrangement as claimed in either Claim 1 or 2, wherein between the two 00 0 coaxial high-frequency cables each coupler is connected with a given power splitting via HF connectors.

4. An arrangement as claimed in Claims 1 to 3, wherein the first section of the first high-frequency cable and the second high-frequency cable are connected via a power splitter to the transceiver station. An arrangement substantially as herein described with reference to Figures 1 4 of the accompanying drawings. i DATED THIS FOURTH DAY OF JANUARY 1996 ALCATEL N.V ABSTRACT An arrangement for transmitting, radiating and receiving high-frequency signals is specified, the said arrangement consisting of a radiating first coaxial high- frequency cable with an outer conductor which has openings over its whole length, and a second coaxial high-frequency cable with a closed outer conductor arranged parallel to the first coaxial cable. The two high-frequency cables 2) respectively are connected by one end to a common transceiving station for high-frequency signals f so 0 and electrically connected to each other at least at one point in its length. For attenuation-free conduction of high-frequency signals, even at high frequencies, the second high-frequency cable has a markedly greater diameter than the radiating high-frequency cable The radiating high-frequency cable is subdivided into at least two sections which are arranged in tandem in the axial direction, and of which a first section is connected to the transceiving station The second high-frequency cable is, with the exception of the first section, connected by the given electrical coupling respectively with at least one of the sections of the radiating high-frequency cable